/Engine/Source/Editor/SequencerCore/Public/MVVM/Extensions/IPinnableExtension.h
Looks for any direct child of RootModel that is pinnable, and reports all their descendants that they are in a pinned branch, to make that lookup faster
static void UpdateCachedPinnedState ( [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FViewModel](API\Editor\SequencerCore\MVVM\ViewModels\FViewModel) > RootModel )